Erratum     

Rudolf H. Steiger  Gorica Harnik-?optrajanova  Emil Zimmermann  Niels Henriksen 《Mineralogy and Petrology》1991,43(4):315-315

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Transport of U in the Opalinus Clay on centimetre to decimetre scales     

Marek Pękala  Jan Dirk Kramers  Hans Niklaus Waber  Thomas Gimmi  Peter Alt-Epping 《Applied Geochemistry》2009

The Opalinus Clay formation in North Switzerland is a potential host rock for a deep underground radioactive waste repository. The distribution of ²³⁸U, ²³⁴U and ²³⁰Th was studied in rock samples of the Opalinus Clay from an exploratory borehole at Benken (Canton of Zurich) using MC-ICP-MS. The aim was to assess the in situ, long-term migration behaviour of ²³⁴U in this rock. Very low hydraulic conductivities of the Opalinus Clay, reducing potential of the pore water and its chemical equilibrium with the host rock are expected to render both ²³⁸U and ²³⁰Th immobile. If U is heterogeneously distributed in the Opalinus Clay, gradients in the supply of ²³⁴U from the rock matrix to the pore water by the decay of ²³⁸U will be established. Diffusive redistribution separates ²³⁴U from its immobile parent ²³⁸U resulting in bulk rock ²³⁴U/²³⁸U activity disequilibria. These may provide a means of estimating the mobility of ²³⁴U in the rock if the diffusion rate of ²³⁴U is significant compared to its decay rate. Sampling was carried out on two scales. Drilling of cm-spaced samples from the drill-core was done to study mobility over short distances and elucidate possible small-scale lithological control. Homogenized 25-cm-long portions of a 2-m-long drill-core section were prepared to provide information on transport over a longer distance. Variations in U and/or Th content on the cm-scale between clays and carbonate-sandy layers are revealed by β-scanning, which shows that the (dominant) clay is richer in both elements.  相似文献   

Pressure-dependent Production Efficiency of an Enhanced Geothermal System (EGS): Stimulation Results and Implications for Hydraulic Fracture Treatments     

Günter Zimmermann  Torsten Tischner  Björn Legarth  Ernst Huenges 《Pure and Applied Geophysics》2009,166(5-7):1089-1106

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Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest   总被引：4，自引：0，他引：4  

Alexander Zimmermann  Sonja Germer  Christopher Neill  Alex V. Krusche  Helmut Elsenbeer 《Journal of Hydrology》2008,360(1-4):87-102

The brief interaction of precipitation with a forest canopy can create a high spatial variability of both throughfall and solute deposition. We hypothesized that (i) the variability in natural forest systems is high but depends on system-inherent stability, (ii) the spatial variability of solute deposition shows seasonal dynamics depending on the increase in rainfall frequency, and (iii) spatial patterns persist only in the short-term. The study area in the north-western Brazilian state of Rondônia is subject to a climate with a distinct wet and dry season. We collected rain and throughfall on an event basis during the early wet season (n = 14) and peak of the wet season (n = 14) and analyzed the samples for pH and concentrations of , Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, , and DOC. The coefficient of variation for throughfall based on both sampling intervals was 29%, which is at the lower end of values reported from other tropical forest sites, but which is higher than in most temperate forests. Coefficients of variation of solute deposition ranged from 29% to 52%. This heterogeneity of solute deposition is neither particularly high nor particularly low compared with a range of tropical and temperate forest ecosystems. We observed an increase in solute deposition variability with the progressing wet season, which was explained by a negative correlation between heterogeneity of solute deposition and antecedent dry period. The temporal stability of throughfall patterns was low during the early wet season, but gained in stability as the wet season progressed. We suggest that rapid plant growth at the beginning of the rainy season is responsible for the lower stability, whereas less vegetative activity during the later rainy season might favor the higher persistence of “hot” and “cold” spots of throughfall quantities. The relatively high stability of throughfall patterns during later stages of the wet season may influence processes at the forest floor and in the soil. Solute deposition patterns showed less clear trends but all patterns displayed a short-term stability only. The weak stability of those patterns is apt to impede the formation of solute deposition-induced biochemical microhabitats in the soil.  相似文献   

Microseismicity induced during fluid-injection: A case study from the geothermal site at Groß Schönebeck,North German Basin   总被引：1，自引：1，他引：0  

Grzegorz Kwiatek  Marco Bohnhoff  Georg Dresen  Ali Schulze  Thomas Schulte  Günter Zimmermann  Ernst Huenges 《Acta Geophysica》2010,58(6):995-1020

The technical feasibility of geothermal power production in a low enthalpy environment will be investigated in the geothermal site at Groß Schönebeck, North German Basin, where a borehole doublet was completed in 2007. In order to complete the Enhanced Geothermal System, three massive hydraulic stimulations were performed. A seismic network was deployed including a single 3-component downhole seismic sensor at only 500 m distance to the injection point. Injection rates reached up to 9 m³/min and the maximum injection well-head pressure was as high as ～60 MPa. A total of 80 very small (?1.8 < M _W < ?1.0) induced seismic events were detected. The hypocenters were determined for 29 events. The events show a strong spatial and temporal clustering and a maximum seismicity rate of 22 events per day. Spectral parameters were estimated from the downhole seismometer and related to those from other types of induced seismicity. The majority of events occurred towards the end of stimulation phases indicating a similar behavior as observed at similar treatments in crystalline environments but in our case at a smaller level of seismic activity and at lower magnitudes.  相似文献   

Der Einfluss der Strömung auf die Zusammensetzung der Lebensgemeinschaften im Experiment     

P. Zimmermann 《Aquatic Sciences - Research Across Boundaries》1962,24(2):408-411

Ohne Zusammenfassung  相似文献   

Thermochemical study of glasses in the system CaMgSi2O6-CaAl2SiO6     

Alexandra Navrotsky  Hans D Zimmermann  Richard L Hervig 《Geochimica et cosmochimica acta》1983,47(8):1535-1538

High temperature solution calorimetry of glasses in the system CaMgSi₂O₆ (Di)-CaAl₂SiO₆ (CaTs) show them to have negative enthalpies of mixing with a regular enthalpy parameter, W_H, of -11.4 ± 0.7 kcal. Negative heats of mixing between alumina-rich and alumina-poor glasses seem to be a general phenomenon in aluminosilicates and are not confined only to glassy systems containing anorthite as a component. The thermodynamic behavior of glasses in the system SiO₂-Ca_0.5;AlO₂-CaMgO₂ appears to vary in a smooth fashion, with small positive heats of mixing near SiO₂ and substantial negative heats of mixing for other compositions. The exothermic behavior with increasing $\text{A1}\text{(Al + Si)}$ may be related to local charge balance of M²⁺ and Al³⁺. The negative heats of mixing in MgCaSi₂O₆-CaAl₂SiO₆, MgCaSi₂O₆-CaAl₂Si₂O₈ and NaAlSi₃O₈-CaAl₂Si₂O₈ glasses are in contrast to the positive heats of mixing found in MgCaSi₂O₆-CaAl₂SiO₆ (pyroxene) and NaAlSi₃O₈-CaAl₂Si₂O₈ (high plagioclase) crystalline solid solutions.  相似文献   

Thermodynamics of plagioclase-melt equilibria in the system albite-anorthite-diopside     

D.J. Henry  A. Navrotsky  H.D. Zimmermann 《Geochimica et cosmochimica acta》1982,46(3):381-391

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